The parent application Ser. No. 07/982,514 filed Nov. 27, 1992, now U.S. Pat. No. 5,310,623 (referred to above) discloses methods and apparatus for fabricating microlenses. A single exposure mask is used to produce a replica of a designed microlens in a photoresist material. The replica is then used to produce the designed microlens in a substrate material.
The method and apparatus disclosed in parent application Ser. No. 07/982,514 filed Nov. 27, 1992, now U.S. Pat. No. 5,310,623, enables a microlens of any configuration to be designed and fabricated.
The design, for example, can be generated by a computer using a three dimensional modeling program. In that event, the modeled microlens is contained within a three dimensional plot having x, y and z coordinates, as illustrated in FIG. 7 of the parent application. The x and y coordinates are divided by lines into a plurality of equal size increments (40 increments of 2.0 micrometers in each coordinate direction in one specific embodiment illustrated in FIG. 7 of the application) so that the lines form a fine grid for locating precise points on the surface of the microlens and for indicating the height (thickness) of the microlens at each precise point.
In the embodiment of the invention shown in FIG. 7-13 of the parent application, the microlens was formed within a single pixel 53. Each pixel 53 was subdivided into sub pixels 55. Each sub pixel was one segment in a rotational symmetry and was divided into gray scale resolution elements 57. In a specific embodiment of the invention disclosed in the parent application, the pixel was 80 micrometers on each side, each sub pixel was two micrometers on each side, and each gray scale resolution element 57 was 0.2 micrometers on each side. The exposing light was ultraviolet light of 0.3 micrometers wavelength.
By using an appropriate mask opening transmission pattern (as shown in FIG. 12 of the parent application), an exposure and a photoresist material could be created which would cause the height of the processed photoresist material to replicate the exact height of the designed microlens. The exposed photoresist material was then processed, using known photoresist processing, to produce in the photoresist material a replica of the desired microlens.
This replica was then used subsequently for producing the desired microlens in a substrate material with the application of known differential ion milling technology.
The present invention utilizes the method and apparatus fabrication features disclosed in parent application Ser. No. 07/982,514, now U.S. Pat. No. 5,310,623, for micro-fabrication of integrated optical devices.
The present invention is particularly directed to methods and apparatus for fabricating within a volume of a photoresist material a replica of a photonic waveguide surface of any designed configuration, using a single exposure mask, and then reproducing the replica directly in a substrate material for ultimate use in photonic applications.
The present invention monolithically integrates selected substrate layers, with certain substrate layers incorporating a specifically designed photonic waveguide surface configuration within the substrate layer.
In some embodiments of the present invention photonic waveguide surface configurations within certain substrate layers (aligned or offset) are constructed to coact with one another in the transmission of photonic electro-optic waves through the substrate layers.